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Appalachiosaurus montgomeriensis

David T. King Jr., Auburn University

A small tyrannosaurid dinosaur, Appalachiosaurus montgomeriensis was indigenous to Alabama and surrounding southeastern states during the Late Cretaceous (about 99 or 100 to 65 million years ago). The name Appalachiosaurus montgomeriensis means "Appalachian lizard from Montgomery." In its day, Appalachiosaurus montgomeriensis was the top predator in the tropical rainforests of the Appalachian foothills and surrounding low plains. The type specimen is the property of the Department of Geology and Geography at Auburn University and is currently housed at the McWane Center in Birmingham, where parts of it are frequently on public display.

Appalachiosaurus montgomeriensisAppalachiosaurus was a predatory dinosaur that lived among a small community of eastern North American dinosaurs in this area. The dinosaur community included duck-billed (hadrosaurian) dinosaurs (Lophorhothon atopus) and at least one species from the nodosaur, ornithomimid, and dromaeosaurid dinosaur groups. During the Late Cretaceous, dinosaurs in what is now the southeastern United States were separated physically from the more diverse (and better known) western North American dinosaur community by a shallow sea that connected the Gulf of Mexico with the Arctic Ocean.

The Appalachiosaurus stood on its hind feet and held its tail more or less straight out behind it as it walked or stood. In this way, the tail was used primarily for balancing. The animal had small front limbs (like its cousin, Tyrranosaurus rex) that were largely useless in normal daily activities. Appalachiosaurus is thought to have had keen eyesight with depth perception and a keen sense of smell. It would have used these senses in hunting prey in the Alabama forests of long ago.

The type specimen on which the name was based was found by Auburn University geologist David King in Montgomery County, Alabama, in July 1982. The bones of Appalachiosaurus montgomeriensis were discovered in a small hill adjacent to a county road in southeastern Montgomery County. During the first excavation, King and a group of Auburn University personnel recovered fragments of skull, limbs, a hind foot, and pelvic elements. A second excavation, conducted by personnel from the Red Mountain Museum of Birmingham (now the McWane Center), uncovered additional bones. In all, the skeleton is about 40 percent complete. Other partial specimens, represented by one bone or a few bones, have been found the Southeast and are held by other museums as well.

Initially, Appalachiosaurus montgomeriensis was identified by its hind limb and foot bones an as an unknown species of the small tyrannosaurid called Albertosaurus, based on comparison with the type specimen of Albertosaurus at the Royal Tyrell Museum in Drumheller, Alberta, Canada. For that reason, it is referred to as Albertosaurus in early publications referencing this dinosaur specimen. More recently, a group of vertebrate paleontologists visited the McWane Center and studied the type specimen in more detail. In a 2005 paper, they determined that the type specimen represented an entirely new genus and species of small tyrannosaurid dinosaur and first used the name Appalachiosaurus montgomeriensis. The type specimen of Appalachiosaurus montgomeriensis is a juvenile that was about two-thirds fully grown. It measured about 23 feet long and probably weighed about 1,300 pounds in life. The gender of this type specimen is unknown. Based on the age of the surrounding rocks, the specimen was determined to have lived about 79 million years ago. The relationship between Appalachiosaurus montgomeriensis and other similar species in the tyrannosaurid group of dinosaurs is currently unknown.

As with all Late Cretaceous eastern North American dinosaurs, the type specimen of Appalachiosaurus montgomeriensis was found in marine sediments, more specifically chalk, made of fine clay and marine plankton that formed at water depths of up to several hundred feet. Scientists believe that Appalachiosaurus montgomeriensis died on land, and then its carcass was washed out to sea, perhaps during a storm. Fossil marine plankton and other marine fossils entombed in the rock with the type specimen and the absence of some heavy bones (which likely fell away as the carcass floated) confirm this finding.

Although paleontological findings of Appalachiosaurus montgomeriensis in museums and laboratories are very scanty, making the age range of its existence difficult to determine, it is likely that this species of dinosaur persisted until the onset of the global ecological catastrophe that is recognized world-wide as coinciding with the demise of the dinosaurs. This catastrophe 65 million years ago led quickly to the extinction of the dinosaurs and many other terrestrial and marine plant and animal groups.

King, David T., Jr., et al. "Stratigraphy and Depositional Environments of the Turnipseed Dinosaur Site in the Upper Cretaceous Demopolis Chalk of Montgomery County, Alabama." Journal of the Alabama Academy of Science 59, no. 2(1988): 34-48.